[request] Sabertooth p67 gop fix

Hi guys,
I have an ASUS Sabertooth P67 combined with an AMD RX 580. I can’t manage to get the card to work in uefi mode, only legacy. I’ve tryed to mod the vga bios with the magic gop but I get no post with efi option for pcie. While looking for a solution I found this post:

could someone perform the same mod on my bios?
I was also planning on buying an external bios flasher just in case, could you suggest me a decent one from aliexpress?

Thanks in advice